Stability of the aryl hydrocarbon receptor and its regulated genes in the low activity variant of Hepa-1 cell line.

Abstract

We examined the expression kinetics of some of the aryl hydrocarbon receptor (AhR)-regulated genes in LA1 variant cells compared to wild type (WT) Hepa-1 mouse hepatoma cell lines, and we investigated the stability of AhR protein as a key step in the function of this receptor. Treatment of both cell types with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) resulted in increased CYP1A1 and CYP1B1 mRNA with a subsequent down regulation of AhR. We show here that co-treatment with transcription inhibitor actinomycin D (ActD) has reversed the TCDD-induced depletion of AhR protein in WT. However, the proteolytic degradation of AhR in absence of TCDD was significantly higher in LA1 cells than in WT, and ActD treatment reduced this loss. Induction of CYP1A1 and CYP1B1 mRNA by TCDD in WT cells each exhibited bursts of activity in the initial hour which were about 3-fold greater than in LAI cells. The induced mRNA levels in LA1 exhibited a slow and sustained increase approximating the WT levels by 20h. The induction of two other AhR-regulated genes also showed comparable turnover differences between the two types of cell. Thus, altered regulation of the AhR responsive genes in LA1 may result from a difference in AhR stability.

• Authors: Andria Humphrey-Johnson, Rawia Abukalam, Sakina E Eltom
• Journal: Toxicology letters (Toxicol Lett) Vol. 233 Issue 2 Pg. 59-67 (Mar 04 2015) ISSN: 1879-3169 [Electronic] Netherlands
• PMID: 25637755 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
• Copyright: Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Environmental Pollutants
• Polychlorinated Dibenzodioxins
• Protein Synthesis Inhibitors
• Receptors, Aryl Hydrocarbon
• Dactinomycin
• Cytochrome P-450 CYP1A1
• Cytochrome P-450 CYP1B1

Topics

• Animals
• Cell Line, Tumor
• Cytochrome P-450 CYP1A1 (biosynthesis)
• Cytochrome P-450 CYP1B1 (biosynthesis)
• Dactinomycin (pharmacology)
• Environmental Pollutants (toxicity)
• Enzyme Induction (drug effects)
• Gene Expression Regulation (genetics)
• Humans
• Kinetics
• Mice
• Polychlorinated Dibenzodioxins (toxicity)
• Protein Synthesis Inhibitors (pharmacology)
• Receptors, Aryl Hydrocarbon (genetics, metabolism)
• Translocation, Genetic